Large earthquake shakes Kilauea Volcano’s south flank

There’s no reason to get all shook up about Wednesday’s magnitude-5.5 earthquake beneath Kilauea Volcano’s south flank, said U.S. Geological Survey scientists at the Hawaiian Volcano Observatory.

The large quake is not a harbinger of an impending eruption nor a precursor to a catastrophic collapse of the volcano. In fact, it had no apparent effect on Kilauea, according to HVO seismic network manager Brian Shiro.

It’s understandable that the earthquake, recorded at 12:55 a.m. Wednesday, might unsettle those familiar with the 2018 lower East Rift Zone eruption in Puna, which destroyed more than 700 homes. Magma pushing into the rift zone, exerting pressure on Kilauea’s south flank, likely set off a magnitude-6.9 earthquake on May 4, one day after the eruption began in Leilani Estates.

Shiro said this week’s temblor occurred at a depth of 4.1 miles on a fault located where the volcano meets the ocean floor. It was centered about 7.5 miles southeast of the Kilauea caldera near the Holei Pali area of Hawai‘i Volcanoes National Park.

There were reports of light to moderate shaking on Hawaii and Maui but no damage, according to the USGS. The agency’s “Did you feel it?” website received over 260 “felt” reports within the first hour of the earthquake.

Shiro said in a news release there were “no detectable changes in volcanic activity at the summit or along the rift zones of Kilauea as a result of this earthquake. Aftershocks are possible and could be felt.”

In fact, as of 5 p.m. Wednes­day, at least a dozen other quakes, none larger than magnitude-2.3 were recorded.

There have been 16 earthquakes of magnitude-5.0 or greater on Kilauea’s south flank during the past 40 years, according to the USGS. Most were caused by “abrupt motion of the volcano’s south flank, which moves to the southeast over the oceanic crust.” Shiro said the data from Wednesday’s magnitude-5.5 temblor indicate it was consistent with a slip along that south flank fault.

Following last May’s magnitude-6.9 earthquake, the USGS moved to squelch speculation and rumors of an impending massive collapse of the volcano, issuing a statement that “geologic history combined with models of south flank motion suggest that the likelihood of a catastrophic failure event is incredibly remote.”

The scientists also noted there have been much larger earthquakes and magmatic intrusions at Kilauea over the last two centuries that were not associated with significant south flank landsliding.

Shiro reiterated that message in an email Wednesday to the Honolulu Star-Advertiser.

For information on recent earthquakes in Hawaii and eruption updates, visit the Hawaiian Volcano Observatory website at volcanoes.usgs.gov/observatories/hvo/.